This invention is directed to a monohydric alcohol-free composition comprising solubilized ethylcellulose. Particularly, this invention is directed to a monohydric alcohol-free composition for topical use on human lips and skin comprising a commercially acceptable carrier and solubilized ethylcellulose. The ethylcellulose being substantially solubilized in at least one solubilizing agent which may be a natural oil, triglyceride propylene glycol ester, neopentyl glycol ester, fatty alcohol or mixtures thereof. The solubilized ethylcellulose is present in a quantity sufficient to enhance the composition's adhesiveness and durability on the lips or skin to which the composition is applied.
The solubilizing agent of the present invention may be substituted or unsubstituted and may be saturated or unsaturated. Additionally the solubilizing agent may be a compound having a solubility parameter .delta.a and .delta.d within the following range: EQU 15.00(J/cm.sup.3).sup.1/2 .ltoreq..delta.d.ltoreq.18.00(J/cm.sup.3).sup.1/2 EQU 8.00(J/cm.sup.3).sup.1/2 .ltoreq..delta.a.ltoreq.10.00(J/cm.sup.3).sup.1/2
wherein .delta.a=.sqroot.p.sup.2 +.delta.n.sup.2 .
The composition of the present invention may comprise more than one solvent to form a mixture of solvents. Said mixture of solvents has a solubility parameter .delta.a and .delta.d within the above-described range.
The invention is advantageous in that the use of the above-described solvent or solvents in combination with ethylcellulose in a cosmetic or pharmaceutical composition enables effective amounts of ethylcellulose to more easily be solubilized into the composition in the absence of monohydric alcoholic solvents, thereby forming improved formulations that are more tolerable by human skin or lips.
The present invention is also directed to a process for preparing cosmetic or pharmaceutical compositions comprising said monohydric alcohol-free composition comprising solubilized ethylcellulose.
Ethylcellulose is an ethyl ether of cellulose, and comprises a long-chain polymer consisting of anhydroglucose units joined together by acetal linkages. It has been observed that solubilized ethylcellulose functions as a hydrophobic film forming agent and a water-insoluble polymer component of cosmetic and pharmaceutical compositions. It has also been observed that inclusion of solubilized ethylcellulose in cosmetic or dermatological compositions enhances the adhesion, durability, viscosity and hydrophobicity efficacy of these compositions.
For instance, the inclusion of solubilized ethylcellulose in cosmetic and pharmaceutical compositions for lips and skin has been found to enhance the adhesion efficacy of such compositions, and hence minimize or alleviate undesirable migration beyond the areas to which these compositions were applied. The extent to which cosmetic or pharmaceutical compositions adhere to its intended surface is an important feature to consumers, particularly in lipstick, lip gloss, and other lip and skin care products.
Further, solubilized ethylcellulose has also been found to enhance the durability efficacy of cosmetic and pharmaceutical compositions applied to lips or skin, and hence improve the wearability of those compositions and may lessen or minimize undesirable transfer to items which may come into contact with the area of the skin or lip on which these compositions were applied. Additionally, solubilized ethylcellulose has also been found to minimize undesirable migration of cosmetics beyond those areas to which the cosmetic was applied, such as lips or a specific area of the skin. Because many compositions for lips and skin contain color and other stain causing agents, the minimization or elimination of undesirable transfer of these compositions is a significant feature to consumers. Solubilized ethylcellulose has further been observed to enhance water resistance, increase film formation on the skin and increase Skin Protection Factor (SPF) activity for sun screens.
However, ethylcellulose has very limited solubility in most solvents found in cosmetic and dermatological compositions. Typically, monohydric alcohols having about 2-8 carbon atoms, such as ethanol, butanol, methanol or isopropanol, are used to more easily solubilize effective amounts of ethylcellulose in a cosmetic or pharmaceutical composition. However, the drawback in using monohydric alcoholic solvents is that they are irritants and volatile, and consequently may be harmful to the skin after repeated use. There is, therefore, a need for a composition, more specifically a cosmetic or pharmaceutical composition, free of monohydric alcohols and having effective amounts of solubilized ethylcellulose contained therein.
Accordingly, it is one object of this invention to provide a composition adapted for topical use on human tissue which is free of monohydric alcohol yet enables substantially all of the ethylcellulose employed to be solubilized in said composition. This is advantageously accomplished by solubilizing the ethylcellulose using one or more of the following solvents, or mixtures thereof: natural oils, C.sub.6 -C.sub.30 triglycerides, propylene glycol esters, neopentyl glycol esters, C.sub.10 -C.sub.100 fatty alcohols, and compounds having a solubility parameter .delta.a and .delta.d within the following range: EQU 15.00(J/cm.sup.3).sup.1/2 .ltoreq..delta.d.ltoreq.18.00(J/cm.sup.3).sup.1/2 EQU 8.00(J/cm.sup.3).sup.1/2 .ltoreq..delta.a.ltoreq.10.00(J/cm.sup.3).sup.1/2
wherein .delta.a=.sqroot..delta.p.sup.2 +.delta.n.sup.2 .
It is a feature of this invention that such compositions are useful in cosmetic applications such as compositions suitable for human lips or skin. Specifically, the lip cosmetic compositions of the present invention are long lasting and exhibit minimal undesirable migration above and below the lip line.
It is another feature of this invention that the compositions of the present invention are useful in pharmaceutical applications, including, but not limited to dermatological applications or compositions which may be used to deliver pharmaceutically effective ingredients via topical administration in humans or animals.
It is another object of this invention to provide a process for preparing such a monohydric alcohol-free composition. This process is accomplished by admixing ethylcellulose and the above-described solvent or solvents so that substantially all of the ethylcellulose is solubilized, while again advantageously avoiding the use of monohydric alcohols to achieve such solubilization. It is another feature of this invention that the process is useful in the preparation of cosmetic compositions. It is yet another feature of this invention that the process is useful in the preparation of pharmaceutical compositions.
It is yet another feature of this invention to provide a process that is useful in the preparation of compositions with improved adhesion and durability efficacies. It is yet another object of this invention to provide a method of enhancing the adhesion and durability of a composition on the lips or skin.